<!DOCTYPE html>
<html>
<head>
  <style>div { color:red; }</style>
  <script src="http://code.jquery.com/jquery-latest.js"></script>
</head>
<body>
  <form><input type="checkbox" /></form>
<div></div>
<script>
  var isFormParent = $("input[type='checkbox']").parent().is("form");
  $("div").text("isFormParent = " + isFormParent);
</script>

</body>
</html>